Power hand tool



Patented July 31, 1928.

UNITED STATES PATENT OFFICE.

EDWIN L. CONNELL, OF CLEVELAND, OHIO, ASSIGNOR TO THE VAN DORN ELECTRIC TOOL COMPANY, OF CLEVELAND,

OHIO, A CORPORATION OF OHIO.

POWER HAND TOOL.

Application led July 26,

ower means for driving home screws,

lts and the like, the general arrangementl being that described and the particular requirement being a ver great speed reduction between the motor an the screw driver blade 2 or bolt head receiving means provided. Ordinarily gearing has been employed in such a tool for the purpose of speed reduction, and owing to the high speeds demanded of the gears the transmission has been nec- 5 essarily noisy in spite of the highest quality of workmanshipv employed. .Moreover, in .a power tool for the purpose described it .1s necessary that provision be made for a slip or give in the transmission operative as the driven object reaches home; the purpose being obviously to insure driving to a tight seat, and yet prevent injury to the tool or work, such as by thread stripping as the seat is reached. For this purpose separate andl comparatively com licated friction or semisitive driving e ements 4have heretofore sen inserted in the transmission.

It is the object of my invention to provide a transmission capable of a great reduction in speed'between the motor and the tool, simple in construction and operation, quiet in operation and employing elements which in themselves perform the clutching function referred to.

The exact nature and particular advantages of my invention will be apparent from the following-description taken'in connection with theaccompanying drawing which is a side elevation of a screw driver chosen for 5 illustration of the invention, the parts shown in operating relation and broken away to show the transmission details. y

The tool shown comprises av base, frame, or casing 1 carrying at its rear end a handle 1928. Serial No. 125,002.

2 within which may or may not be mounted a motor controlling switch o erated bythe trigger 3, and terminating ownwardly in an opening 4 vfor the electric motor cable running to thesource of power supply. In the central part of the Casin 1 is a motor, details of which are not s own, but the rotor` shaft 5 of which projects through a partitioning web 6 into a cup shaped compartment forward of the motor and closed by the cover plate 1a in which the transmission is located. A fan 11 may be mounted upon the rotor shaft for motor cooling purposes. Forward of tlie transmission is a bearing 7 1n which a tool carrying member 8 is mounted for rotation, the outer end of the tool carrying member being provided with the usual chuck 9 to receive the screw driver blade 10 and the rear lportion of the tool carrying member extendin into the transmission housing portion o the casing in a manner to be described. The general strucl ture so far' described is old ...and common practice in the art.

I The rotor shaft 5 is carried in a bearing 12 in the partition, the\bearing being provided with the packing 13 to prevent the lubricating medium in the transmission chamber from entering the motor portion of the tool, and the end of the motor shaft terminates forwardly in the pinion 14. Meshing with this pinion is a gear 15` carried upon a counter-shaft 16- mounted to rotate in an inwardly projecting portion of the casing and carrying at its opposite end the gear 17 of somewhat larger diameter than the gear 15. f

Upon the .tool carrying member 8 are mounted for free rotation thereon a pair of driving members 18 and 19 rovided with the corresponding conical driving surfacemm.s indicated.

Each of the members 18 and 19 is provided with a flange, preferably integral as shown, in which are cut gear teeth, those upon the member 18 meshin with the gear 17 and those upon the mem r 19 meshing directly with the pinion 14 the pitch diameters of the flange gears being preferably equal. It will be evident therefore that rotation of the motor will eect rotation of the members 18 and 19 in opposite directions and at different speeds. ixed upon the tool carrying member 8 is a spider 20 provided with fingers extending between the driving surfaces of the members 18 and 19. Lyingbetwecn the driving surfaces referred to and spaced by the fingers of the spider 20 are a number of rolling 'planeta elements 21 slightly conical Ato correspon with the surfaces, the prolongation of any rectilinear element of any of these `surfaces passing through a point common to all the elements and lying 1n the axis of the member-,8,

The member 19 is backed with respect to the casing 1 by the thrust bearing 25. The member 18 is backed against a shoulder upon the member 8 by the thrust bearing 22. The member 8 is normally urged outwardly of the casing 1 bythe spring 23 positioned coaxially with the tool carrying member 8 by a turned down end portion of the member and the depression indicated in a cap member 24 which is screw threadedinto a shank portion of the member 19 whereby the member 19 is longitudinally positioned against the thrust bearing 21.

Thus by the `arrangement described the inward motion of the tool carrying member 8 is opposed by the spring 23, and limited by the action of the rollers 21 between thedriving surfaces of members 18 and 19, inward thrust of the tool being transmitted through the thrust bearing 22 and the driving niember 18 acting through the rollers against the member 19 backed upon the frame through the thrust bearing 21; and outward motion of the tool lcarrying member is limited by contact of the thrust bearing 22 against the end of the bearing 7, acting through the member 18 and the spider 20, fixed upon the tool carrying member.

Operation of the tool is as follows: Upon grasping the tool by the handle 2, depressing the trigger 3 to cause actuation of the motor the driving members 18 and 19 are rotated as described in opposite directions and at speeds diii'ering slightly, the speed of the member 18 being somewhat greater than that of the member 19 owing to the gear 17 being of somewhat greater diameter than the gear 15. At this time there is no rotation of the blade 10 since owing to the spring 23, the driving members 18 and 19 are maintained apart sutiiciently so that the rollers 21 do not contact with either of them with enough force to be moved thereby,

Maintainig the motor in rotation the screw driver blade is next inserted in the slotted head of the screw to be driven and the tool forced against the screw whereupon the parts assume the position shown in the drawing.' That is, the member 8 moves inwardly against the spring 23 to cause the rollers 21V to be tightly engaged between the driving surfaces of the members 18 and 19. As the pressure is first applied the rollers slip somewhat upon the driving surfaces. However, as the pressure reaches a navales certain point the surfaces close upon the rollers with force enough to prevent slipage and effect their rotation. Although as escribed, .the member 18 is rotating in a counter-clockwise direction and at a greater speed than that of member 19 yet owing to tie greater mean diameter of the driving surface of the member 19 the rollers will be caused to move each in a clockwise direction upon its own axis and at such a s eed with respect to the member 18 that all o the rollers will move bodily in a clockwise direction about Vthe axis of the member 8. This bodily movement of the rollers is transmitted through the fingers of the spider 20 to the member 8, thus causing movement of the screw blade in a clockwise direction to drive the screw and at a speed very much slower than that of the motor.

As the screw reaches home its resistance to rotation increases to a point suiiicientl to cause slippage of the rollers upon the driving surfaces an the screw driver blade stops turning whereupon the tool is removed from the screw thus releasing the ressure upon the rollers and allowing the lade to remain motionless.

The material of the rollers may be either metal, or of a hard -brous nature, the latter under light loads, being quieter in operation and affording smoother engagement and better traction; the angularity of the cones varying somewhat with the materials of the rollers as compared with that of the members 18 and 19.

It will be apparent that the arrangement described is of a planetary type, the speed of the screw driver blade when the driving surfaces are functioning, being the differential or resultant of the independent speeds of the driving members 18 and 19. It will also be noted however, that the'driving sur` faces not only provide an eiicient speed reducing medium, but serve as a friction clutch whereby the drive is automatically engaged, varied or disengaged by pressure of the tool against the driven screw.

While I have specicially illustrated a screw driver, it is obvious that a bolt head receiving member could as well be substituted for the screw driver blade shown, and that the tool would then be equally adapted to drive and properly seat bolts, the functioning of the tool parts being unaltered; and that similarly other threaded articles could be accommodated and manipulated; and that in fact my invention would have equal application in any hand tool wherein similar speed reduction and clutching functions would be desirable. l It is equally obvious that my invention comprehends the use of rolling planetary elements other than the conical rollers illustrated. For instance balls might be preferable in certain instances, in which case lll) the members 19 and 18 would be formed as cup or cone respectively as well known in the art.

I would also call attention to my choice of proportions in the example illustrated. By making the parts 18 and 19 of equal diameter, it is possible to-assemble or remove the parts 18, 19, 20 without disturbing the shaft 16 or parts immediately associated therewith, and a mostcompact arrangement of the entire transmission is effected.

What I claim is:

1. In a tool of the class described, motor means, a pair of members having driving surfaces, driving connections between said motor means and said members whereby said members are driven at dfffering speeds, a tool carrying member, and planetary element-s engageable between said driving surfaces and having driving connection with said tool carrying member.

2. In a tool of the class described, a frame, a tool carrying member mounted for rotation therein, a pair of members rotatably mounted on said tool carrying member and having driving surfaces, means for rotatin said surfaced members at ldiffering spee s, and planetary elements engageable between said driving surfaces and having driving connection with said tool carrying member.

3. In a tool of the class described,l a casing, a tool carrying member rotatably mounted therein, a pair of members rotatably mounted on said tool carrying member and having driving surfaces vand toothed portions, planetary elements engageable be- 1 tween said driving surfaces fand having driving connection with said tool carrying member, a countershaft having geared connection with the toothed portion of one of said surfaced members, and motor means having geared connection with said countershaft and with the toothed portion of the other of said surfaced members, the arrangement being such that said surfaced members are driven in opposite directions and at differing speeds.

4. In a tool of the class described, a casing, a tool carrying member rotatably mounted therein, a pair of members rotatably mounted on said tool carrying member and having driving surfaces and toothed portions, planetary elements engageable between sad driving surfaces and having driving connection with said tool carrying member, a countershaft having geared connection with the toothed portion of one of said surfaced members, and a high speed motor secured with said casing and having a pinion, said pinion having geared connection with Svsaid countershaft and arranged to latch with the toothed portion of the other` of said surfaced members, whereby said surfaced members are driven in opposite directions and at differing and relatively low speeds.

In testimony whereof I hereby affix my signature.

EDWIN L. CONNELL, 

